Kaiser study: Cancers more likely for HIV-positive

MEDICINE

Published 4:00 am, Wednesday, November 23, 2011

People with HIV infections have a higher risk of developing certain cancers than those who aren't infected, and the sicker they are, the greater their risk, according to a large study of Kaiser Permanente members.

The study, results of which were published Tuesday, provides further evidence of the possible benefits of treating HIV-positive patients with antiretroviral therapy soon after they're diagnosed - while they're still symptom-free and before the virus has a chance to dramatically weaken their immune systems, HIV/AIDS experts said.

The Kaiser study showed that the weaker the immune system, the more vulnerable a patient is to cancer. But researchers also found that even HIV-positive people with relatively healthy immune systems had higher rates of certain cancers, suggesting that they could reduce their risk of cancer if they started drug treatment immediately and shored up their immunity.

"Ideally you would want a clinical trial and look at the question of starting people earlier, and if that reduces their burden of cancer," said Michael Silverberg, lead author of the study and a research scientist with the Kaiser Permanente Division of Research in Oakland.

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"The pendulum is swinging toward earlier therapy," he said. "Not all patients are willing to do earlier treatment, but giving patients all the information available might be very useful."

Silverberg's paper was published in the current issue of Cancer Epidemiology, Biomarkers and Prevention.

Opening for cancer

Doctors have long known that HIV infection is associated with an increased cancer risk, especially for cancers known to be caused by viruses such as Kaposi's sarcoma and non-Hodgkin's lymphoma. As HIV attacks the immune system, patients become increasingly vulnerable to other viruses and, in turn, cancer.

That scientists are even talking about the link between HIV and cancer shows how far medical treatment has come, Silverberg said. "Twenty-five years ago, if you talked about the kind of cancer research we're doing now, people would have been happy," he said.

For many years, before antiretroviral therapies became widely available and were shown to greatly reduce HIV's attack on the immune system, most people with HIV infections died before cancer could become a concern.

Doctors have been aware of an increased cancer risk in HIV-positive patients for a while, but just how much of a risk hasn't been well defined. Doctors also have struggled to separate the risk of cancer related to HIV's attack on the immune system from the behaviors that can increase the odds of getting cancer and tend to go hand in hand with HIV/AIDS, such as smoking and drinking alcohol or having unprotected sex.

The Kaiser study is among the first, and largest, to compare cancer rates between HIV-positive individuals and people who aren't infected but are similar demographically. The study looked at 20,000 HIV-positive Kaiser members in California and compared them with 215,000 members who were not infected.

HIV-positive patients had higher rates of Kaposi's sarcoma, non-Hodgkin's lymphoma, Hodgkin's lymphoma, melanoma, and anal and liver cancer. Neither smoking nor drinking appeared to be a factor in any of those cancers other than liver.

Their risk was increased as much as 200 times in the case of Kaposi's sarcoma, a rare cancer that is highly associated with HIV and AIDS. Other cancers ranged from a 40 percent increased risk for liver cancer and a 55-fold increase for anal cancer. For reasons that doctors don't yet understand, the risk of developing prostate cancer is slightly reduced with HIV infection.

Other risk factors

HIV-positive patients who smoke or drink too much alcohol have a slightly increased risk of developing lung or liver cancer compared with uninfected people who are smokers and drinkers.

The risks increased dramatically in patients whose T-cell counts - a measure of the strength of the immune system - fell below 200. A healthy person will have a T-cell count of at least 600, and the national guidelines for treating HIV infection are to start antiretroviral therapy when the count drops below 500.

But the Kaiser study also showed that rates of at least five types of cancer were higher even in HIV-positive individuals with T-cell counts of 500 or higher. That suggests, some doctors and public health experts said, that early drug treatment that keeps T-cell counts near the level of an uninfected individual may help prevent some cancers.

"This adds to the increasing literature that supports earlier treatment," said Dr. Grant Colfax, director of HIV prevention at San Francisco's Public Health Department, which encourages drug treatment as soon as people are diagnosed with HIV, instead of waiting for the virus to attack their immune systems.

Colfax added that the study underscores the need to get HIV-positive patients to stop smoking and cut back on their drinking, and in general embrace healthy lifestyle choices beyond just treating the viral infection.

"That's changed from the days when life expectancy was dramatically reduced and in terms of people's priorities, smoking cessation might not have been high on the agenda," Colfax said. "But certainly these data reinforce that now more than ever it's of critical importance."